The operating principle of an inductive sensor is based on the variation of coupling between a primary winding and secondary windings of a transformer operating at high frequency and without using a magnetic circuit. The coupling between these windings varies according to the position of a moving (electrically) conductive part, generally called the “target”. Currents induced in the target in fact modify the currents induced in the secondary windings. By adapting the configuration of the windings and knowing the current injected in the primary winding, measuring the current induced in the secondary windings makes it possible to determine the position of the target.
In order to integrate such an inductive sensor in a device, notably an electronic device, it is known to produce the transformer mentioned above on a printed circuit board. The primary winding and the secondary windings are then constituted by tracks formed on the printed circuit board. The primary winding is then for example supplied by an external source and the secondary windings then carry currents induced by the magnetic field created by a current flowing in the primary winding. The target, which is a conductive part, for example made of metal, can have a simple shape. It can for example be a part cut out from sheet metal. In order to produce a linear sensor, the cutting for producing the target is for example rectangular whereas, for a rotary sensor, this cutting will be for example in the shape of an angular sector, the radius and angle of which are adapted to the movement of the part.
Generally, two sets of secondary windings are designed to produce sine and cosine functions of the position of the target over a complete travel of the sensor. Such functions (cos and sin) are well known and can be processed easily by an electronic system. By forming the ratio of the sine to the cosine and then by applying an arctangent function, an image of the position of the target is obtained. The argument of the sine and cosine functions is a linear (or affine) function of the position of the target whose travel then represents a greater or lesser portion of the spatial period of these trigonometric functions.
In order to obtain measurable induced currents reliably, it is preferable to have either a large number of turns or turns of large size. The second option is not compatible with the production of a compact sensor. Because of this, it is generally chosen to have a large number of turns.
In order to limit the space occupied on the printed circuit board, the present invention proposes producing turns to form the secondary windings on two separate layers.
In order to do this, it is appropriate to produce vias passing through the printed circuit board to allow the connection of the turns thus produced.
A purpose of the present invention is to propose an arrangement of turns for producing secondary windings of an inductive position sensor which is easy to implement.
Another purpose of the invention is to propose an arrangement making it possible to limit, for a given number of turns, the number of vias to be produced in the corresponding printed circuit board.
Advantageously, the turns will be able to be arranged in a compact manner in order to limit the overall dimensions of the sensor.
In order to facilitate the use of measurements made at the level of the secondary windings, the proposed arrangement will preferably make it possible to have a substantially constant distance between the different turns of the secondary windings and the primary winding.